1. Field of the Invention
The invention relates generally to the conversion of carbon dioxide to hydrocarbons and more particularly to a catalytic process for the conversion of carbon dioxide to hydrocarbons.
2. Description of the Related Art
Processes have been proposed for the conversion of carbon dioxide to hydrocarbons. The prior art processes generally comprise a number of reaction steps.
DE 101 56 975 A1 discloses a four-step process. In the first step carbon dioxide is isolated from the earth's atmosphere. In the second step water is dissociated by electrolysis into hydrogen and oxygen. In the third step the carbon dioxide is reacted with the hydrogen to form carbon monoxide and water. In the fourth step a mixture of the carbon monoxide and additional hydrogen is converted to hydrocarbons and water.
DE 203 20 020 U1 discloses an integrated plant for the production of cement and hydrocarbons. Electric energy from a nuclear plant is used to dissociate water to form hydrogen. Carbon dioxide is reacted with hydrogen in a reverse water gas shift reactor to form carbon monoxide, which in turn is reacted in a Fischer-Tropsch reactor to form hydrocarbons.
A similar process (reverse water gas shift reaction of carbon dioxide and hydrogen, followed by a Fischer-Tropsch reaction) is disclosed in US 2005/0232833.
GB 2 418 430 A discloses a process in which carbon dioxide is enriched from the atmosphere, or a carbon dioxide rich flue gas is used. Carbon dioxide is reacted with hydrogen to hydrocarbons in a Fischer-Tropsch reaction. The document does not disclose how the carbon dioxide/hydrogen mixture is converted to the syngas feedstock required for the Fischer-Tropsch reaction.
GB 2 459 430 A discloses a process wherein carbon dioxide is extracted from the atmosphere by chemical and physical extraction. The carbon dioxide is subjected to catalytic hydrogenation in the presence of hydrogen obtained from electrolysis of water. In one embodiment carbon dioxide is reacted with hydrogen to methanol; in turn, methanol is converted to hydrocarbons in a Fischer-Tropsch process. In a second embodiment carbon dioxide is reacted to octane using two catalysts, a salt in addition to a nickel hydrogenation catalyst.
U.S. Pat. No. 4,339,547 discloses a process in which carbon dioxide is extracted from the atmosphere, for example using NaOH to form Na2CO3. Hydrogen is produced by electrolysis. Carbon dioxide is reacted with hydrogen over a copper catalyst to form methanol. Methanol is converted to hydrocarbons over a zeolite catalyst.
WO 00/25380 discloses a process for storing solar energy. In the process solar energy is converted to electric energy using photovoltaic cells. The electric energy is used in electrolysis to form hydrogen. The hydrogen is reacted with carbon dioxide to form methanol, which is used as a fuel in a methanol fuel cell to generate electric energy.
WO 99/20713 discloses an intricate process in which carbon dioxide generated in the combustion of a fossil fuel, such as methane, is reacted with hydrogen in a Sabatier reactor over a nickel catalyst.
WO 2007/108014 discloses a process in which carbon dioxide from an industrial combustion process is reacted with hydrogen from water electrolysis to form methanol. The methanol is converted to hydrocarbons in the Mobil methanol-to-gasoline (MTG) process.
Thus, there is a particular need for an improved catalytic process in which carbon dioxide sequestration is combined with its catalytic conversion. There is a particular need for such a process that uses a renewable energy resource for the production of hydrogen.